Biodiversity & Conservation

Common flat periwinkle - Littorina obtusata

Littorina obtusata

Image Peter Barfield - Littorina obtusata. Image width ca 4 cm.
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Distribution map

Littorina obtusata recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

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Littorina obtusata is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Mollusca Snails, slugs, mussels, cockles, clams & squid
Class Gastropoda Snails, slugs & sea butterflies
Authority Linnaeus, 1758
Recent synonyms Littorina littoralis
Map icon Recorded Distribution in Britain and Ireland Common to all shores where brown seaweeds occur on all British and Irish coasts.
Habitat information icon Habitat information The flat periwinkle is almost always associated with fucoid algae, in particular Ascophyllum nodosum, Fucus serratus and Fucus vesiculosus from mid to lower tidal levels on rocky shores and occasionally into the sub-littoral. It is tolerant of low salinities and a wide range of exposure.
Text page icon Description A small periwinkle (up to 1.5 cm in height), it has a flattened spire and large tear-drop shaped aperture. The last whorl makes up about 90% of the height of the shell and the outer lip joins the body a little below the apex. The shell appears smooth but upon closer inspection is found to be finely reticulate. It is highly variable in colour (from olive green to yellow to banded and chequered patterns) depending on its habitat, with lighter shells being found in more sheltered shores. It may be confused with Littorina fabalis (syn mariae) in which the aperture is larger than the body whorl and the spire is even flatter.
Identifying features
  • Up to 1.5 cm in height.
  • Body whorl slightly larger than aperture.
  • Flat topped with minimal spire.
  • Variable colour, can be olive green, yellow, brown or patterned.
Additional information icon Additional information Littorina obtusata lays whitish oval or kidney shaped egg masses on Ascophyllum nodosum, Fucus serratus and Fucus vesiculosus, and sometimes on rock surfaces. It takes up to four weeks for crawling young to emerge.

This review can be cited as follows:

Paolo Pizzolla 2008. Littorina obtusata. Common flat periwinkle. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 22/05/2012]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=3714>